Fix blurry FontImageSource icons in iOS Tab Bar and buttons

[japarson]

Description of Change

We are not properly scaling the iOS icons:

var scale = destinationContext.Window?.Screen?.Scale ?? 1;

The issue here is that on the first render, the Window is null, so we use a scale of 1 instead of e.g., 3. We can instead get the Window and scale through MauiContext. In the tab bar, we weren't using a scale at all.

Issues Fixed

Fixes #6043
Fixes #14728

[japarson]

@jknaudt21 Can you point out any documentation that needs to be added?

[jknaudt21]

@jknaudt21 Can you point out any documentation that needs to be added?

Not really. A lot of Maui.Platform doesn't get displayed in the docs (don't know why), so there's nothing here that stands out.

That being said, you could always take the opportunity to document UpdateSourceAsync 😋

[jknaudt21]

Looks good to me! Aside from seeing if Windows should also receive the same fix (you already mentioned this in the comments), my only recommendation would be to add a test to check that that image's scale matches that of the IMauiContext. Not sure if that's even possible, but might we worth a try.

[mattleibow]

I think I also had a start with this, but no idea what state it is in: https://github.com/dotnet/maui/pull/14807/files

One difference I see is that I used an optional window method, so I am wondering if there are situations where there is no window yet.

Also, does this respond to density/scaling changes? Like on macOS you update the display scale?

[PureWeen]

One difference I see is that I used an optional window method, so I am wondering if there are situations where there is no window yet.

I don't think so, the MauiContext you use for this stuff only comes into existence if there's a window.

We could still keep the code in place here

https://github.com/dotnet/maui/pull/16864/files#diff-a209ad18263c1c3effbd89b25fff7dbe248270890bb057f2564180cb0b7550b5L32

That defaults to one if no windows is set though.

Maybe it can log a warnings?

Also, does this respond to density/scaling changes? Like on macOS you update the display scale?

Not really sure how to achieve this right now. Image does this because we inherit from UIImageView but we can't inherit from UIButton. Perhaps we just need to wrap all our UIButtons so we can get life cycle events from them.

[mattleibow]

Looks OK generally, maybe some thoughts:

• we should probably avoid API shanges
• Maybe use the ubiquitous GetDisplayDensity() on all platform windows to get the density as it is a uniform API and supports windows' unique features.

[jfversluis]

@japarson you're still OK processing the feedback and taking this home? If not, please let us know so we can look at it! Thanks!

[japarson]

@japarson you're still OK processing the feedback and taking this home? If not, please let us know so we can look at it! Thanks!

Yep, working on it. Just had to wait for a couple PRs from Matt and Shane.

[mattleibow]

looks good.